This invention relates to a hydraulic damper and more particularly to improvements in hydraulic dampers of the type comprising a cylinder containing therein hydraulic fluid, a piston working in the cylinder and dividing the interior thereof into two chambers, a piston rod secured to the piston and extending to the outside of the damper, and a damping force adjusting device operable from the outside of the damper to change or adjust the damping force of the damper.
In one of the prior art hydraulic dampers of this type, the damping force adjusting mechanism is mounted on the side wall of the damper. The damper works satisfactorily, however, the construction of the damper is complicated, and due to its size the damper cannot be installed in a restricted space.
Another prior art hydraulic damper of this type comprises a hollow piston rod having a rod member extending co-axially therethrough, and a valve body connected to the inner end of the rod member. By actuating the rod member from the outside, the damping force is adjusted by changing the effective area of a passage connecting the both chambers. An actuating mechanism such as an operating knob or the like is installed on the upper end of the damper, however, there are shortcomings in that the adjustment cannot be effected easily and that the dust, water or the like will accumulate on the mechanism thus limiting the durability of the damper. Further, it has been difficult to effectively adjust the passage area based only on known parametric conditions outside of the damper.